X-ray mirrors of various types have long been used in some x-ray scattering instruments to provide a means of focusing x-rays and improving flux and intensity, relative to pin-hole optics, by increasing the angular acceptance of the system with respect to the x-ray source. These methods for enhancing intensity have not found widespread application in x-ray scattering instruments because they lack spatial compactness, and flexibility in use, and are awkward to align. In the case of x-ray optical systems, simultaneous high-resolution in wavelength, angular collimation and spatial extent are usually achievable only at the expense of considerable loss in flux and intensity.
An early proposal for an x-ray collimator consisted of two glass plates facing each other at a small angle. This principle was extended in a conical x-ray guide tube proposed by Nozaki and Nakazawa [J. Appl. Cryst. (1986) 19,453].
In a recent paper, Yamaguchi et al [Rev. Sci. Instrum. 58(1), Jan. 1987, 43], there has been proposed a two dimensional imaging x-ray spectrometer utilizing a channel plate or capillary plate as a collimator. It is apparent that Yamaguchi et al are treating the channel plate as a large aperture device acting solely as a set of Soller slits consisting of an array of channels surrounded by opaque walls.